The runoff (rainfall) and sewage waters of New Orleans have been
going, untreated, into Lake Pontchartrain since the city began.  The
present inflow probably will create only a short-term blip in the
pollution curve of the lake's waters.  Most of those esthetically-
pleasing broad avenues in New Orleans are that wide because they
were originally open drainage canals, but during 1940-1970 the
canals were enclosed as concrete conduits and covered over with
soil and broad avenues, the canal waters still draining, untreated, to
the lake and river.  Many canals remain open.

During the late 1950s, when I grew up in New Orleans, our main
swimming beach on the lake had weekly samples taken for coliform
bacteria counts.  It was discovered that the area had been
contaminated for a couple of years, but that no one was responsible
for doing anything with the bacterial reports except to file them
away.  The city then put a sign at the bathing area, "This Beach
Is/Is Not Safe for Swimming Today" -- the "Is" or "Is Not" section
with a movable cover, depending on the result of the prior week's
bacterial count.  The municipal population and industrial waste
disposal have increased significantly since then, but most runoff
still discharges without treatment.

Presumably, the remaining molluscan populations in the lake are
adapted to this constantly fluctuating environment and should be
able to survive (at least, recuperate in a few years) from this
relatively short-term onslaught of contamination.  Lake
Pontchartrain has a constant inflow of fresh water on its northern
side, so the waters are only mildly saline as the fresh mixes with
higher salinity marine inflow from the Gulf of Mexico on the eastern
side.  Higher rainfall (as from hurricanes) to the north of New
Orleans decreases the lake's average salinity and flushes out more
of the polluted waters from New Orleans.

From about 9000 feet up in the Andes, in Quito, Ecuador,
Howard (botanist/ecologist -- Kate is the malacologist/ecologist)
>>
Howard L. Clark or Kate Clark .
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